Ash content is an important indicator of hydroxypropyl methylcellulose. Many customers often ask when they understand hydroxypropyl methylcellulose: what is the ash value? Hydroxypropyl methylcellulose with a small ash content means higher purity; cellulose with a large ash content means that there are many impurities in it, which will affect the use effect or increase the amount of addition. When customers choose hydroxypropyl methylcellulose, they often directly light some cellulose with fire and burn it to test the ash content of the cellulose. But this detection method is very unscientific, because many manufacturers add combustion accelerants to the cellulose. On the surface, the cellulose has very little ash after burning, but in practice, the water retention of hydroxypropyl methylcellulose is not very good.

So how should we correctly detect the ash content of hydroxypropyl methylcellulose? The correct detection method is to use a muffle furnace to detect.

Instrument Analytical balance, high temperature muffle furnace, electric furnace.

Experiment procedure:

1)?First, put a 30ml porcelain crucible in a high-temperature muffle furnace and burn it at (500~600) °C for 30 minutes, close the furnace gate to lower the temperature in the furnace to below 200°C, then take out the crucible and move it to a desiccator to cool (20~30) min, weighing.

2)?Weigh 1.0 g of hydroxypropyl methylcellulose on an analytical balance, put the weighed sample into a crucible, then place the crucible containing the sample on an electric furnace for carbonization, cool to room temperature, add sulfuric acid (0.5-1.0) ml, and put it on the electric furnace for complete carbonization. Then move to the high temperature muffle furnace, burn at (500~600) ℃ for 1 hour, turn off the power of the high temperature muffle furnace, when the furnace temperature drops below 200 ℃, take it out and put it in the desiccator to cool (20~30) min, and then weighed on an analytical balance.

Calculation Ignition residue is calculated according to formula (3):

m2-m1

Ignition residue (%) = ×100………………………(3)

m

In the formula: m1 – the mass of the empty crucible, in g;

m2 – mass of residue and crucible, in g;

m – the mass of the sample, in g.